1. Field of the Invention
This invention relates to a sheet feeding apparatus mounted in an image forming apparatus such as a photocopier, a printer, and the like.
2. Description of Related Art
As an image forming apparatus such as a photocopier, a printer, etc., a mechanism has been proposed in which a sheet feeding means is set in containing multiple sheets to automatically feed the sheets and after a pickup roller takes up the sheets, a feed roller and a retard roller cooperate to convey the sheets one by one to form images. Another known apparatus conveys sheets fed manually one by one to form images, in order for feeding differently sized sheets and special sheets such as thick papers and envelops.
To render such an image forming apparatus smaller, a conveying means for conveying sheets that are fed from a sheet containing means is also made smaller, and thereby, the radius of curvature of a curving portion in a conveying route is made relatively small as to be capable of conveying merely the regular cut sheets that are ordinarily used. With such a conventional art, however, when automatically feeding a special sheet such as a rigid thick sheet or envelop, the apparatus cannot feed the sheet along a sheet guide forming a curving portion due to a small radius of curvature at the curving portion in the conveying route, thereby raising a problem that the apparatus fails to stably feed sheets upon occurrence of paper jams or conveyance defects.